Sphere Online Judge (SPOJ)

list of classical problems

ID	NAME	USERS	ACC %	DIFFICULTY C I
3970	Convert to Decimal Base System	55	38.74	17 17
3972	Stargates	47	13.60
3981	Shortest Regular Bracket	81	33.92
4003	Subway planning	43	18.98
4004	Exploding CPU	139	45.77
4008	Con Voi	9	57.69
4010	Chặt cây	10	21.31
4021	Bipalindrome	183	30.77
4034	Pizza Delivery	53	16.55
4052	Game	75	29.27
4060	A game with probability	208	21.97
4062	Rob Mini-Safe	113	39.49
4069	Morphing is Fun	29	18.85
4070	Two Professors	102	13.96
4083	Tele Broadcast	67	50.52
4097	Locomotive	35	38.30
4142	Ellipse	17	8.37
4154	IZBORI	36	24.54
4156	PLAHTE	68	35.51
4160	A1 Road	88	50.21
4178	Distance on a square lattice	121	53.06
4185	Cube	55	36.14
4188	Amazing equality	41	13.45
4189	Landing	5	3.03
4202	Brackets Parade	236	44.87
4210	Fast Maximum Matching	16	47.73
4211	Fast Maximum Flow	19	23.81
4212	Another Longest Increasing Subsequence Problem	14	46.15
4225	Payment System	29	66.07
4275	rotate it	40	55.70
4278	Battlefield	6	25.00
4307	Stamps	28	40.24
4308	Byteantean towns	55	24.08
4309	Circular game	33	19.79
4311	Quasi-template	59	34.07
4324	The fate of the pineapple	42	28.95
4361	Connected Points	8	28.95
4378	Twofive	64	29.46
4407	Counting Arborescence	101	33.94
4410	Repair the Door	59	22.46
4411	Counting Expressions	29	35.63
4414	Highway	53	20.96
4420	Counting Graphs	72	36.93
4421	Irreducible polynomials over GF2	63	18.03
4453	Bouncing Balls II	224	27.81
4455	Going to the Movies	88	36.56
4459	Muzidabutur	34	27.56
4461	A Famous Airport Manager	25	16.75
4477	Flower growing	114	21.98
4478	Counting Expressions II	14	32.73